Question 1178853
f the scores for three tests are 96, 98, and 86,
 what must the scores on a fourth test be to make the average 90
:
let x = the score of the 4th test
:
{{{((x + 96 + 98 + 86))/4}}} = 90
{{{((x + 280))/4}}} = 90
Multiply both sides by 4
x + 280 = 360
x = 360 - 280
x = 80 score will give an average of 90 
:
You can confirm this, add up the 4 scores and divide by 4